Temperature sensing elements have electrical characteristics that vary with temperature. By observing or measuring an electrical characteristic, the temperature of the temperature sensing element can be determined. For example, where the temperature sensing element is a thermistor that has a resistance that varies with temperature, temperature can be measured by determining the resistance of the thermistor. Conventional temperature sensing systems include any of several techniques for measuring electrical characteristics. In some conventional systems, the characteristic is directly measured. The resistance of the thermistor, for example, can be determined by measuring a voltage drop across the thermistor for an associated current flow. Such systems are limited, however, since the components and reference levels used for measuring must be accurate and reliable. In many devices utilizing temperature measuring systems, the low tolerance measuring components and additional components required to maintain a reliable reference value, such as a voltage, are prohibitively expensive. Other techniques include discharging or charging a capacitor through a reference resistor, charging or discharging the capacitor through the thermistor, and comparing the times to charge or discharge each component to determine the resistance of the thermistor. This conventional technique is limited in that the accuracy of the measurement depends on the values used for the resistor and capacitor. Accordingly, the accuracy of the temperature measurements are degraded where the capacitor value or resistor value vary over temperature, time, or between components. In addition, the accuracy of the measurement depends on the supply voltage used to charge the capacitor.
Accordingly, there is a need for an apparatus, system, and method for determining a temperature of a temperature sensing element.